For years, scientists and health organizations have touted the use of sunscreen everyday, every time we go outside. As health professionals, we have probably preached these beliefs hundreds of times.  Sometimes science has taken it even further than limiting sun exposure and using sunscreen.  The deejays on a morning radio program recently joked about a study which showed that wearing heavy clothing in the summer decreased the risk of skin cancer more than sunscreen.  Not exactly the type of fabric we all want to wear when it’s 95 degrees outside.

Then recently, a few research studies contradicted this long-held belief.  Reports came out that some ultraviolet (UV) exposure and the associated increase in production of vitamin D may prevent serious, internal cancers.  All of us summer-fun lovers let out a collective cheer.  Could it be that Saturday afternoons at the pool are good for us?  Do I no longer have to feel guilty when I don’t apply SPF487 before my afternoon dog walk?

USA Today (I know, not a reputable health publication, but still interesting) published the following information¹:

• Several studies observing large groups of people found that those with higher vitamin D levels also had lower rates of cancer. For some of these studies, doctors had blood samples to measure vitamin D, making the findings particularly strong. Even so, these studies aren't the gold standard of medical research — a comparison over many years of a large group of people who were given the vitamin with a large group who didn't take it. In the past, the best research has deflated health claims involving other nutrients, including vitamin E and beta carotene.
• Lab and animal studies show that vitamin D stifles abnormal cell growth, helps cells die when they are supposed to, and curbs formation of blood vessels that feed tumors.
• Cancer is more common in the elderly, and the skin makes less vitamin D as people age.
• Blacks have higher rates of cancer than whites and more pigment in their skin, which prevents them from making much vitamin D.
• Vitamin D gets trapped in fat, so obese people have lower blood levels of D. They also have higher rates of cancer.
• Diabetics, too, are prone to cancer, and their damaged kidneys have trouble converting vitamin D into a form the body can use.
• People in the northeastern United States and northerly regions of the globe like Scandinavia have higher cancer rates than those who get more sunshine year-round.

Of course, there are a few considerations before you (and your students) swear off sunscreen.  Sun exposure, without sunscreen, should be limited to less than 15 minutes several times per week.  Melanoma, basal cell carcinoma, squamous cell carcinoma, and premature aging are still serious implications of too much sun.  In the winter, regardless of length of exposure, sunshine probably won’t provide enough vitamin D to make a difference due to the sun’s angle.  Those of us in northern states or with darker skin may not get enough Vitamin D throughout the year.  Unless you eat a fatty fish, such a salmon, on a daily basis, a vitamin D-3 supplement might be just what the doctor ordered.

While experts are not ready to recommend forgoing sunscreen, this research takes us one step further to understanding the link between nutrition and cancer prevention.  For now, enjoy the sun as you enjoy life’s other pleasures—in moderation.

1   USA Today. Vitamin D research may have doctors prescribing sunshine. Available at: http://www.usatoday.com/news/nation/2005-05-21-doctors-sunshine-good_x.htm